Non functioning CD DVD drive

Hello Folks
I seldom use either my CD or DVD drives but occasionally I do need to do so and I expect them to work when asked. My problem is that neither now work properly. Both read OK but the DVD won't let me write to it at all and my CD drive insists I log on as an Administrator before I can burn a CD.
Both come up with the error E:\ (or D as the case may be) is not accessible. Incorrect function, if I'm logged on as 'User' . I have tried installing the DVD drive in Device Manager and letting Windows XP install on rebooting but the fault remains. I seem to remember something about having to actually disconnect the ribbon cable from the drive units but am unsure as to the sequence of events and if I should reboot with the drives disconnected, and shut down again before reconnect in the ribbon cables to the drive. This is Windows XP sp2 that I'm using and as I say the drives play perfectly well and in My Computer recognise the presence of a disc (even a blank) disc when installed, but I'm having this trouble writing to the disc. Can anyone please give me a lead here? I suppose I should say that last time I needed to use these drive they worked perfectly well, but that might well be a year ago!